Development of Resistant Coating Systems Based on Polymer Binders

Carbon fiber reinforced plastics are widely used in areas of technology requiring high specific properties of the products (specific strength and rigidity), chemical resistance, and elevated heat resistance. An increase in the mechanical properties of such plastics can be obtained by increasing the adhesion of the polymer binder to the carbon fibers, and this adhesion in turn depends substantially on the state of the surface of the fibers. Studies have been published dealing with the surface activation of carbon fibers by liquid-phase [1, 2] and gas-phase [3] oxidants; this makes it possible to increase the bonding strength in the carbon-fiber-binder system and, correspondingly, the strength of carbon fiber reinforced plastics. However, the indicated methods of surface treatment of carbon fibers either are expensive (ozonization) or involve the use of chemically corrosive liquids which cause corrosion of the equipment and give rise to unfavorable working conditions. In the present work, we studied the effect of surface treatment of carbon fibers from Ural-LO-24 (TU 6-06-31442- 85) hydrated cellulose with atmospheric oxygen on the properties of thermoplastic carbon fiber reinforced plastics. The polymer matrix used was 21030 polypropylene GOST 26996-86. The carbon fiber reinforced plastics were prepared by combining the polymer matrix and carbon fibers chopped into segments up to 10 mm in a multiple-unit extruder at a temperature of 473-493 K. During the surface treatment, the carbon fibers were held in a furnace in an atmosphere of air at temperatures of 673-873 K. In addition to the surface treatment of the carbon fibers, the latter were also dressed with an aqueous solution of polyvinylpyrrolidone with a molecular mass of 12,600. The results of the study of the strength of carbon fibers subjected to surface treatment with atmospheric oxygen showed that above 873 K, a substantial loss of fiber mass (> 5%) and a decrease of their breaking strength are observed. At temperatures of 673-823 K, an increase in strength is observed that may be due to the burning out, during the treatment of the carbon fibers, of foreign surface deposits and defect regions, and to a decrease in the number of dangerous cracks on their surface. A similar dependence was found in a study of the properties of composites obtained from polypropylene and surfacetreated carbon fibers (Fig. 1). Oxidation of carbon fibers by atmospheric oxygen causes an increase in the strength and rigidity of the composites. The optimal treatment time of the reinforcing filler was 15-20 min at 823 K (Table 1). The increase in the strength of the composite is explained by a strengthening of the carbon fibers as a result of the improvement of their structure. Also possible is the formation on their surface, during the treatment, of active oxygen-containing groups; this results in an increased adhesive interaction of the binder and filler and an increase in the tensile strength of the composites. Surface oxidation of carbon fibers also results in the formation of a brittle layer on their surface; this causes a decrease in the impact elasticity of polypropylene-based carbon-reinforced plastics (see Table 1) and in some cases limits the areas of their application. The same effect has been observed earlier in the reinforcement of thermosetting binders with surface-treated carbon fibers [4]. To reduce the drop in impact elasticity of the composites by producing on the surface of the carbon fibers an intermediate layer having an affinity for the polymer binder and filler, the fibers were dressed with an aqueous solution ofpolyvinylpyrrolidone. The optimal amount of dressing deposited on the fiber was determined to be 2 mass %. Table 2 lists the values of the properties of carbon-fiber plastics reinforced with dressed carbon fibers and also with carbon fibers oxidized with atmospheric oxygen, then dressed. Analyzing the tabular data, one can conclude that the maxi

Background: The technological developments for nanocellulose production from cheaper plant materials compared to wood, in particular, agricultural waste is an urgent task of nanobiophysics. The discovery of possibility of expanding the functional characteristics of materials in compositions with modified cellulose particles essentially stimulated the interest of researchers in cellulose composites. Surface modification of cellulose particles by functional materials, such as dyes, metal oxides, silicon, allows applying composites with modified cellulose in various areas of modern industry. A significant improvement in the operational performances of functionalized cellulose particles can be achieved by using them as filler in polymers. Epoxy resin compositions with modified and unmodified cellulose particles, studied in present work, are an example of hybrid biosystem. The interfacial interaction of filler particles with the epoxy matrix, their concentration and dispersion can change the physical and chemical properties of the biopolymer and the functional parameters of biocomposites. Studying the influence of external fields on the physical and chemical properties of epoxy resin-based biosystems and their influence on operational parameters seems to be an urgent problem of advanced and sustained materials science. Objectives: The purpose of this work was to develop an effective nanocellulose synthesis from plant materials and surface functionalization of micro- and nanocellulose particles with clathrochelate iron (ΙΙ) dye as well obtaining biocompositions of epoxy resin with functionalized and non-functionalized micro- and nanocellulose, and to explore of the morphology, chemical resistance, mechanical and thermal properties of epoxy composites with cellulose micro and nanoparticles. Materials and methods: The studying objects were the composites of epoxy resin Eposir-7120 with a polyethylene polyamine “PEPA” hardener in a ratio of 6.2:1 and 10% cellulose micro and nanoparticles. The microcellulose obtained from wood has been a commercial product. Nanocellulose has been synthesized from organosolv cellulose obtained from Miscanthus x giganteus stalks. Surface modification of micro- and nanocellulose was performed using the clathrochelate iron (ΙΙ) dye. The specific surface area of cellulose particles was determined using low-temperature nitrogen adsorption-desorption according to the Brunauer-Emmett-Teller method. Mechanical parameters were determined using universal Shopper and UMM-10 machines. Thermal analysis was performed using Q1500 analyzer. Swelling was determined by the gravimetric method. Results: Elastic modulus E, compressive strength σ and thermogravimetric parameters were determined. It was shown that in composites with micro and nanocellulose the E rises in 7.0–12.2% while the σ increases in 9.1% for composites with cellulose micro particles. The loading resin with nanocellulose and modified cellulose microparticles no affects the σ value of composites. The thermal stability of epoxy polymer (310°C) reduces after loading with micro and nanocellulose to 290 and 300°C, respectively. Chemical resistance of composites with both celluloses to 20% nitric acid reduces. In neutral medium swelling characterizes by rapid sorption to saturation of 15–20% acetone in 36 hours. Conclusions: Thus, the synthesis method of nanocellulose from plant materials and functionalization of its surface with clathrochelate iron (ΙΙ) were developed. Light response of dye was detected in visible spectral range. Epoxy resin composites with 10% micro and nanocellulose were obtained. The filling effect with micro- and nanocellulose at elastic modulus, compressive strength, and thermal stability of epoxycomposites was studied. The swelling processes run similarly in composites with cellulose micro and nanoparticles.

Structures requiring chemical resistance are usually coated with surface protecting agents, but the cost for maintenance and re-construction is incurred due to the low durability. Therefore, in this study, sulfur was polymerized and the performance was examined so that it could be used as the concrete surface protecting agents for structures requiring chemical resistance. The evaluation results indicated that for the spray of the sulfur polymer surface coating agents, the application of the gravity type was appropriate; and for the number of coating times, about 3 cycle spray gave the best results. For the surface condition of the concrete to be coated with the surface protecting agents, outstanding quality was obtained above room temperature (), and the bond strength increased as the temperature increased. The evaluation results of the strength characteristics depending on the filler content of the surface protecting agents indicated that about 20~40% filler mixing contributed to the strength improvement as it reduced the shrinkage of the sulfur polymer. Also, the mixing of silica showed larger increase in the bond strength than the mixing of fly ash, and the most outstanding bond strength characteristics could be obtained by the mixing of both silica and fly ash. In the case of the chemical resistance, the strength reduction was minimized and outstanding chemical resistance was obtained when the fly ash and silica were substituted by 20%, respectively. The performance evaluation of the chloride ion penetration indicated that for the specimens coated with the sulfur polymer surface protecting agents, the chloride ion penetration resistance increased by 29~48% compared to the specimen without the coating of the surface protecting agent. The examination of the coating condition of the surface protecting agents, compressive strength, bond strength, chemical resistance, and salt damage resistance indicated that in the range of this study, the optimal level was when the silica and fly ash were substituted by 20%, respectively, as the filler for the sulfur polymer.

This paper describes the theoretical analysis and experimental research work on composite propellants for their mechanical and rheological properties. The theory of the polymers rheology has been described to model the polymer properties. The theory is extended to the composite propellants comprising of a polymer binder filled with solid oxidizer and metallic fuel. The variations in the oxidizer particle size and its distribution have been studied experimentally to analyze the effect on the performance properties. The results of propellant viscosity and mechanical properties have been measured and discussed. It was concluded that fine AP particles act as active fillers and enhance the mechanical properties of composite propellants. Viscosity decreases with increase in the amount of fine AP particles and then starts increasing when fine proportion increases beyond 20~25 percent. Similarly elongation increases with increase in fine AP particle size and maximum value is obtained at fine AP contents of 25~35 percent. Size of the AP mean diameter also affects the mechanical properties. Both mechanical strength and elongation substantially decrease as the mean AP particle size increases. I. Introduction HE composite solid propellants are composed of a polymeric binder with high solid loads of oxidizer and a metallic fuel with some additives. The relationship between the formulation variables and different properties of composite propellants are highly complex and interrelated. The knowledge on different dependencies and availability of modeling tools can be of significant help for propellant developers and analysts. Much research work has been carried out on these propellants since their use in the middle of last century. In spite of many achievements thereafter, design of a propellant formulation is yet considered as an art and almost all of the practical formulations are developed through working knowledge and practical experience. The propellant performance can be characterized with respect to specific impulse, density, gas composition, flame temperature and a number of thermochemical properties using the computer programs 1 . However, the variation of important performance parameters such as burning rate, mechanical and bonding properties, and processing characteristics with variation in formulation cannot yet be presented by mathematical models. These properties are changed with raw materials, solids shape, particle size and its distribution, and even changing the source of raw materials. Many studies have been reported previously to correlate the individual performance properties with the formulation parameters 2~7 . Most of these efforts are based on empirical relationships. Rheology is the science and technology of deformation of polymeric or plastic materials. The polymeric binder imparts main physical and chemical properties to the propellant. The composite propellant properties can be modeled by applying the concept of polymer rheology. Conventional polymers and rubbers filled with solid particles have previously been studies based on this theory 8 , while no such work has previously been reported on the composite propellants at least in the open literature. In the present study the theory and concepts of physical chemistry of polymer rheology are applied to understand and model the propellant properties such as viscosity and mechanical properties. The paper presents both the theoretical and experimental work on the effect of solid fillers in the propellant on the performance properties. In the experimental work, the results of mechanical properties (tensile strength, elongation, and modulus) and viscosity were measured for different formulations. These results have been analyzed and the discussed based on the theory of polymer rheology for the highly filled rubbers and polymers.

Practical Analysis Techniques of Polymer Fillers by Fourier Transform Infrared Spectroscopy (FTIR)

Surface and bulk characterization of an ultrafine South African coal fly ash with reference to polymer applications

The production of monodisperse inorganic nanoparticles attracts the attention of researchers around the world due to their potential importance in practical applications in the field of optical devices, catalysts, drug delivery, fillers for polymers, etc. One such material is silicon dioxide, which serves as the basis for a huge number of nanocomposites. In this regard, the aim of this work is to study the effect of the type of dispersion medium on the synthesis of nanosized SiO2. The paper presents the results of an investigation of the influence of the type of solvent on the morphology, the structure and size of silicon dioxide particles synthesized by sol-gel method. It was found that the type of solvent significantly affects the shape, size of the particles, their aggregation and stability. The particles of SiO2 synthesized by the Stober method are monodisperse and X-ray amorphous regardless of the type of solvent and contain a significant amount of adsorbed molecules of alcohols and water.

Recently, water-soluble and aqueous polymers (water-based polymers) have attracted much attention as binders for lithium ion batteries (LIBs) because of the need for low-cost materials and environmentally compatible electrode fabrication processes. For example, N-methyl-2-pyrrolidone (NMP), which is listed as a carcinogenic chemical with reproductive toxicity is often used as a solvent to prepare a slurry (cathode material particle/conducting carbon additive/conventional polyvinylidene difluoride (PVdF) binder/ NMP solvent) employed in the fabrication process of electrode films on current collectors; this slurry should be recycled without releasing it to the atmospheric environment. Therefore, switching from a nonaqueous-based fabrication process to an aqueous-based process has been widely investigated. The hurdles in developing water-soluble and aqueous polymer binders for use in cathodes in LIBs are still high; improvements are necessary to increase the resistance to electrochemical oxidation and dissolution of metal oxide surfaces in water. In order to overcome these problems, a variety of polymer materials have been applied in the fabrication of cathodes with water-based slurries. In recent years, Li-rich solid-solution layered cathode materials comprising layered LiMO2 (M: transition metals) and Li2MnO3 have attracted much interest because some materials exhibit capacities as high as 250 mAh g-1 in the voltage range of 2.0 and 4.8 V. These materials are charged to above 4.5 V (vs. Li/Li+) to fully activate the Li2MnO3 component, and after activation, the cathodes are charged to 4.5 V to reach discharge capacities over 250 mAh g-1. To use these promising high-voltage and high-capacity cathodes in the next-generation Li-ion batteries prepared in environmentally compatible electrode fabrication processes with a water-based binder, water-based binders having high resistances to electrochemical oxidation during charging process should be developed. In this study, an aqueous hybrid polymer (TRD202A, JSR), which was composed of acrylic polymer and fluoropolymer, was selected as a binder for the Li-rich solid-solution layered cathode material Li[Ni0.18Li0.20Co0.03Mn0.58]O2. A cathode prepared with Li[Ni0.18Li0.20Co0.03Mn0.58]O2 particles, TRD202A binder, CMC and conductive carbon additive was tested and analyzed for charge/discharge capacity, cycle stability, rate performance, mechanical resistance, resistance of electrochemical oxidation, and changes of the surface composition and structure after water-treatment used for preparing water-based slurry. The water-based TRD202A cathode binder is a water-based emulsion and is designed with a unique hybrid polymer developed from acrylic polymer and fluoropolymer to satisfy both the requirements of high adhesion and chemical and electrochemical resistances. Wu and co-workers have already reported an application of the TRD202 binder in a Li-rich solid-solution cathode. They mentioned that the TRD202A binder can be used for high-voltage cathodes in the voltage range of 2.0-4.6 V [1], and its thermal stability is equivalent to that of PVdF. However, they have not examined the water-based binders for charge/discharge capacities, long cycle stability, rate performance, mechanical resistance, resistance of electrochemical oxidation, or changes of the surface composition and structure after water-treatment used for preparing the water-based slurry. We have examined in depth the above points with the Li-rich solid-solution cathode (3/5)Li2MnO3·(1/5)Li[Ni0.5Mn0.5]O2 ·(1/5)Li[Ni1/3Co1/3Mn1/3]O2. [1] Wu Q, Ha S, Prakash J, Dees DW, Lu W (2013) Electrochim. Acta 114:1-6

Links between flow properties and formulation of powders of 100 and 500 µm mean particle sizes were investigated. To determine the influence of surface treatment, the flow properties of glass beads were analyzed after various surface treatments leading to hydrophilic, hydrophobic, and lactose-coated surfaces. Furthermore, to investigate the influence of powder core composition, agglomerated lactose powders of circa 100 and 500 µm mean particle size were also produced by high-shear wet granulation and characterized. Hydrophilic and hydrophobic surface treatments did not alter surface topography and particle size distribution, whereas lactose-coated glass beads and agglomerated lactose powders presented noticeable changes of surface structure and particle size increase. Furthermore, all 100 µm powders were classified as easy flowing; hydrophobic glass beads and agglomerated lactose presented the highest and lowest powder flowability, respectively. For 500 µm powders, hydrophilic glass beads and agglomerated lactose powders had the highest and lowest flowability, respectively. The poorer flowability of agglomerated lactose may arise from their angular shape, their higher width of particle size distribution, the lower core density and the higher cohesion of lactose-coated particles. Last, no significant difference of powder compressibility was observed and all studied powders were hardly fluidizable, due to their high particle weight.

Impact of dietary solvents on flexural properties of bulk-fill composites

A single-element interferometer for measuring refractive index of transparent liquids

This study evaluated the effect of post-printing polymerization time on residual monomer elution and water sorption in a 3D-printed resin composite. Eighty samples were fabricated and assigned to four groups based on post-curing duration: 0, 20, 40, and 60 min. Each group was subdivided according to two storage conditions (distilled water and 75% ethanol–water solution), and evaluated at 1 and 7 days. High-performance liquid chromatography (HPLC) quantified eluted monomers. Additionally, 40 specimens underwent a 4-month sorption/desorption cycle for water sorption and solubility assessment. Data were statistically analyzed using kernel regression (monomer data) and Welch ANOVA (water sorption and solubility) at a significance level of p < 0.05. BisEMA was the only monomer detected, with significantly higher elution recorded in ethanol-based storage. Increasing post-curing time notably reduced both monomer release and water sorption/solubility (p < 0.001); however, the optimal results were observed at 40 min post-curing. These findings suggest that extending post-curing beyond an optimal threshold does not further improve composite properties, underscoring the importance of identifying precise curing parameters in order to enhance durability and material performance.

In this paper, the waste polyethylene terephthalate (PET) was glycolysed by trimethylolpropane with zinc acetate as catalyst. The effects of different content glycolysis product of waste PET on the appearance, viscosity, particle size and molecular weight of autoxidative water-reducible alkyd resins and the corresponding film adhesion, flexibility, impact resistance, gloss, hardness and chemical resistance were studied. Meanwhile, experimental results were compared with commercial water-reducible alkyd and water-reducible alkyd without the glycolysis product of waste PET. The results show that the maximum concentration of PET in autoxidative water-reducible alkyd resins can reach 8.5 wt%, and the molecular weight, particle size and viscosity of water-reducible alkyd resin do not change much with the increase of PET concentration. The introduction of PET resulted in the viscosity of water-reducible alkyd resins being greater than that of water-reducible alkyd resin without PET; this is mainly because PET contains harder terephthalic acid monomer units. However, the particle size of water-reducible alkyd resins with waste PET is significantly lower than that of the water-reducible alkyd resin without PET; this is due to PET-free water-reducible alkyd resin containing more pentaerythritol with greater steric hindrance. In addition, the hardness of the water-reducible alkyd resin paint film (PET content is 8.5%) reaches 1H, which is higher than the hardness (HB) of the water-reducible alkyd resin paint film without PET and the commercial alkyd resin paint film, while the physical properties and chemical resistance of the former are comparable to those of the latter two kinds of paint films. Therefore, the use of waste PET in water-borne coatings systems not only reduces the cost of coatings, but also opens up a new market for recycled PET, which may contribute a promising method for management of waste PET.

The shear stiffness of granular material at small strain levels is a subject of both theoretical and practical interest. This paper poses two fundamental questions that appear to be interrelated: (a) whether this stiffness property is dependent on particle size; and (b) whether the effect of testing method exists in terms of laboratory measurements using resonant column (RC) and bender element (BE) tests. For three uniformly graded types of glass beads of different mean sizes (0·195 mm, 0·920 mm and 1·750 mm), laboratory tests were conducted at a range of confining stresses and void ratios, using an apparatus that incorporates both RC and BE functions and thus allows reliable and insightful comparisons. It is shown that the small-strain stiffness, determined by either the RC or BE tests, does not vary appreciably with particle size, and it may be practically assumed to be size independent. The laboratory experiments also indicate that the BE measurements of small-strain stiffness are comparable to the corresponding RC measurements, with differences of less than 10%. Furthermore, the BE measurements for fine glass beads are found to be consistently higher than the RC measurements, especially at large stress levels, whereas this feature becomes less evident for medium-coarse glass beads, and eventually diminishes for coarse glass beads. The study indicates that the characteristics of output signals in BE tests can be largely affected by the frequency of the input signal, the mean particle size of the material and the confining stress level, and that these factors are interrelated. Improper interpretation of wave signals may lead to shear stiffness measurements that are unreasonably low, either showing a substantial increase with particle size or showing the opposite. A micromechanics-based analysis assuming the Hertz–Mindlin contact law is presented to offer an understanding of the size effect from the grain scale.

The chemical environment is one aspect of the oral environment, which could have an appreciable influence on the in vivo degradation of composite restoratives. The effects of chemical media on surface hardness of four composite restoratives (Silux [SX], Z100 [ZO], Ariston [AR] and Surefil [SF]) were investigated. The relationship between hardness and the thickness of the degradation layer was also studied. Thirty six specimens (3 x 4 x 2 mm) were made for each material. Following polymerization, the specimens were stored in artificial saliva at 37 degrees C for 24 h. The specimens were then randomly divided into six groups of six, subjected to microhardness testing (load = 500 gf, dwell time = 15 s) and stored in the following chemicals for 1 week at 37 degrees C: artificial saliva (S), distilled water (W), 0.02 N citric acid (C), 0.02 N lactic acid (L), heptane (H) and 75-25% ethanol-water solution (E). After conditioning, the specimens were again subjected to hardness testing and sectioned. Change in hardness (DH) was computed and the thickness of the degradation layer (DL) was measured using a computerized image analysis system at 600x magnification. Results of statistical analysis (ANOVA/Scheffe's [P < 0.05]) of DH based on materials were as follows: SX - E > all other mediums; ZO - W > C; and AR - S, W, E > H (> indicates significantly greater hardness change). No significant difference in DH was observed between the different chemicals for SF. The effects of chemical media on DH were found to be material dependent. A significant but weak positive correlation (Pearson's correlation [P < 0.05]) exists between change in hardness and thickness of the degradation layer.